The present invention relates to a positioning and clamping system which is suitable in particular for positioning and clamping a workpiece-carrying pallet on a pallet receiving table. The system comprises at least two conical supports arranged spaced from each other on the pallet receiving table and at least two tapered sleeves, adapted to cooperate with the conical supports, which are connected to the pallet on the side which is to be located on the table.
It is known to mount workpieces which have, for example, to be machined in metal or plastics material processing operations in a machining procedure with various machines, on pallets, to allow quick and precise replacement of the workpiece together with the pallet at the machining location of a machine with a subsequent workpiece, without further disassembly or assembly of the workpiece itself. As a result of using a pallet on which the workpiece is mounted, it is necessary that only the pallet and not the workpiece itself is clamped or unclamped at the machining location in order to produce the machining position of a workpiece. A quick-change system of the workpiece of this type has proved to be particularly advantageous in machining centres with more than one machine machining the workpiece.
The pallet to be clamped is positioned and securely clamped with the workpiece located thereon to a machining table or a pallet receiving table which can be located at or on a machine tool. Such positioning must be able not only to take place extremely precisely as the exact machining of the workpiece is dependent on the precise positioning, but it must also be easy to carry out, like the clamping of the pallet, wherein it should be noted that the region of the pallet receiving table is generally heavily soiled by shavings and lubricating oil or liquid coolant.
The advantage of using a pallet for clamping a workpiece is that the pallet has consistently uniform connection geometry with respect to the workpiece which is replaced, and therefore very quick positioning and clamping of the workpiece relative to the working spindles of the machine tools is possible owing to this consistent connection geometry.
The pallets can have a size of, for example 800×800 mm to 800×1000 mm.
The machining or pallet receiving table can be designed as a circular table which has a pallet mount which is rotatably mounted in the substantially vertically oriented axis of rotation.
Known pallet clamping stations consist, for example, of two pins which are arranged on the machining table in a common plane and which are received in correspondingly arranged bushes on the underside of the pallet. A planar system of this type allows the pallet to be fixed in a plane, wherein the height of the pallet to be positioned is determined by the placement thereof on the machining table.
An arrangement for positioning a pallet on a machining table is also known in which four cones are arranged on the machining table. With a cone angle of approximately 60° the cones are relatively flat and have a diameter of approximately 80 mm. There are tapered sleeve-shaped bushes on the underside of the pallet corresponding to the cones arranged on the table which are to cooperate with the cones. Furthermore, there are clamping jaws on each cone for clamping of the pallet which are intended to avoid slippage of the pallet on the machining table after it has been positioned. Owing to the quadruple arrangement of the cones, which, moreover, also allow positioning perpendicular to the plane of the table as well as in the plane of the table, such a system is twice four times over defined. This means that measuring inaccuracies in only one of the four cones can render the entire arrangement inaccurate. In other words precise fixing of the pallet on the machining table is no longer possible. Such a measuring inaccuracy of only one cone can occur owing to the simple fact that additional layers, such as impurities, have been deposited on the cone surface of one cone to a greater extent than on the cone surface of the adjacent cone.
It is an object of the present invention to provide improved positioning and clamping of workpiece-carrying pallets on a pallet receiving table of a machine tool or in machining centres in such a way that over definition of the entire arrangement is not possible, but quick, precise and simple positioning of the pallet on the pallet receiving table and reliable and secure clamping of the pallet to the pallet receiving table is possible, and to overcome the given disadvantages of the systems according to the state of the art.